JPH0864537A - Vapor growing method - Google Patents

Abstract

PURPOSE: To reduce the n-type carrier on the interface between a compound semiconductor growing film and a substrate, after feat-treating an InP substrate meeting specific heating requirement under the atmosphere comprising PH3 and H2 in a specific flow rate, the growing step of a compound semiconductor layer is to be started under reduced pressure. CONSTITUTION: A compound semiconductor layer is grown by vapor deposition on an InP substrate in a growing vessel under reduced pressure of 10-150Torr. In this process heat-treating the InP substrate at the temperature between 630 deg.C and 700 deg.C for longer than 10 minutes under the atmosphere comprising PH3 and H2 in the flow rate of PH3 exceeding 0.50SCCM/cm<2> per unit area of the growing vessel under the pressure reduced atmosphere of 10-150Torr, and then the growing step of the compound semiconductor layer is started. Otherwise, after heat-treating the InP substrate at the temperature between 670 deg.C and 700 deg.C for longer 10 minutes under the atmosphere comprising PH3 and H2 in the flow rate of PF3 exceeding 0.30SCCM/cm<2> , the growing step of the compound semiconductor is started.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a vapor phase growth method,
For example, the present invention relates to a technique useful when applied to a low pressure MOCVD method (metal organic chemical vapor deposition method) of vapor-depositing a compound semiconductor layer of InP, AlInP, GaInAs or the like on an InP substrate under a reduced pressure atmosphere of about 10 to 150 Torr.

[0002]

2. Description of the Related Art InP, AlInP, G on an InP substrate
As a method of vapor-phase growing a compound semiconductor layer such as aInAs, there is a MOCVD method in which an organic metal is used as a raw material of a group III element and a hydride such as AsH ₃ or PH ₃ is used as a raw material of a group V element. In this method, in order to prevent the group V element having a large vapor pressure from being dissociated from the substrate during the substrate heating until the InP substrate reaches a predetermined growth temperature before the vapor phase growth is started, the inside of the growth container is heated during the substrate heating. To P
The phosphorus pressure was applied to the InP substrate by supplying H ₃ . Then, when the substrate temperature reached a predetermined growth temperature, an organic metal gas or the like was supplied into the growth container to start vapor phase growth.

However, conventionally, there has been a problem that n-type carriers are generated at the interface between the compound semiconductor layer grown as described above and the InP substrate. On the contrary,
A technique has been proposed in which n-type carriers at the interface are reduced by subjecting an InP substrate to a heat treatment at a growth temperature or higher for 30 minutes or longer in a PH ₃ atmosphere before vapor-depositing a compound semiconductor layer (Japanese Patent Laid-Open Publication No. Sho. 64-57711 and J.
Appl.Phys.71 (8), 15 April 1992, pp3898-3903). According to this proposal, normal pressure (1 atm, or 7
In the case of the atmospheric pressure MOCVD method in which the film is grown under 60 Torr), the Si concentration at the interface can be reduced by performing a heat treatment at 640 ° C. for 30 minutes or more, whereby the n-type carriers at the interface are reduced or It is said to disappear.

[0004]

However, the technique described in the above-mentioned Japanese Patent Laid-Open No. 64-57711, etc. has become mainstream in recent years because the thickness and composition uniformity of the grown film and the crystallinity are good. In the low pressure MOCVD method in which film growth is performed under a reduced pressure of about 30 Torr, it has been revealed by the following experiments conducted by the present inventor that the effect of reducing n-type carriers at the interface described above is not exhibited.

That is, the present inventor has found that the same temperature (660 ° C.) and the same PH as the growth conditions of the InP buffer layer that is normally grown on the InP substrate before growing the compound semiconductor layer.
After the substrate was heat-treated at a reduced pressure of 30 Torr for various treatment times of 30 to 60 minutes with ₃ amounts, TM was placed in the growth chamber.
InP film was grown on the substrate by flowing I (trimethylindium). Then, when the n-type carrier concentration at the interface between the growth film and the substrate was measured, no decrease in n-type carriers was observed.

The present invention has been made in view of the above circumstances, and an object thereof is to reduce the n-type carriers at the interface between the growth film and the substrate under a reduced pressure atmosphere of about 10 to 150 Torr. InP, AlInP, GaInA on top
Another object of the present invention is to provide a vapor phase growth method capable of vapor-phase growing a compound semiconductor layer such as s.

[0007]

In order to achieve the above object, the present inventor has conducted extensive studies and, as a result, has found that the treatment temperature of the heat treatment to be performed before the start of vapor phase growth under reduced pressure is usually the InP buffer layer. The growth temperature (660 ° C.) of the InP buffer layer, or the flow rate of PH ₃ is higher than the flow rate during the normal growth of the InP buffer layer, or by performing them simultaneously, the interface between the growth film and the substrate is increased. It has been found that the n-type carrier can be reduced.

The present invention has been made based on the above findings, and in vapor-depositing a compound semiconductor layer on an InP substrate in a growth container in a reduced pressure atmosphere of 10 to 150 Torr, the invention according to claim 1 The flow rate of PH ₃ per unit cross-sectional area of the growth container is 0.50 SCCM / cm ² or more, and the atmosphere is composed of PH ₃ and H ₂ and is 630 ° C. or more 70
In the invention according to claim 2, the flow rate of PH ₃ per unit cross sectional area of the growth container is 0.30 SCCM /
67 in an atmosphere consisting of PH ₃ and H ₂ that is at least cm ^2.
At a temperature of 0 ° C. or higher and 700 ° C. or lower, in the invention according to claim 3, in an atmosphere composed of PH ₃ and H ₂ in which the flow rate of PH ₃ per unit cross-sectional area of the growth container is 0.50 SCCM / cm ² or more. After subjecting the InP substrate to a heat treatment at a temperature of 670 ° C. or higher and 700 ° C. or lower for 10 minutes or longer, the growth of the compound semiconductor layer is started.

[0009]

According to the invention described in claim 1, the flow rate of PH ₃ is 0.5.
A temperature of 630 ° C. or more and 700 ° C. or less as 0 SCCM / cm ² or more, and the flow rate of PH ₃ is 0.3 in the invention of claim 2.
A temperature of 670 ° C. or higher and 700 ° C. or lower as 0 SCCM / cm ² or higher, and the flow rate of PH ₃ is 0.5 in the invention of claim 3.
The InP substrate is heat-treated at a temperature of 670 ° C. or higher and 700 ° C. or lower at 0 SCCM / cm ² or higher, and then I
By vapor-depositing a compound semiconductor layer of nP, AlInP, GaInAs, or the like, the number of n-type carriers existing at the interface between the growth film and the substrate is reduced as compared with the conventional case.

[0010]

EXAMPLES The experiments conducted by the present inventor and their consideration will be described below to clarify the features of the present invention. The present invention is not limited to the experiments described below.

First, the present inventor has found that the heat treatment temperature and PH ₃
The InP substrate is heat-treated under a reduced pressure atmosphere by variously changing the flow rate of I, and then I
An experiment was conducted to grow an nP film. The processing conditions of each sample were as shown in the time chart of FIG. 1 and Table 1.

[Table 1]

(Sample 1) In the time chart of FIG. 1, the temperature pattern is (A) and the PH ₃ supply pattern is (a). That is, while the flow rate of PH ₃ which is twice the flow rate Vp 2 of PH ₃ during growth of the InP buffer layer is flown into the growth chamber, the substrate is grown at the growth temperature T 1 of the InP buffer layer.
After holding at temperature T2 (680 ℃) higher than (660 ℃) for t1 hour (900sec), t2 time (300sec)
After that, the substrate temperature is lowered to T1 and then TMI supply is started, and PH3 is supplied after t3 time (300 seconds).
Was reduced to Vp2.

(Sample 2) P with temperature pattern (A)
The H ₃ supply pattern was set to (b). That is, while maintaining the flow rate of PH ₃ preoccupied Vp2, after holding t1 hours the substrate at temperature T2, the substrate temperature over time t2 lowered to T1, and then starting the supply of TMI.

(Sample 3) P as temperature pattern (B)
The H ₃ supply pattern was set to (a). That is, the substrate temperature is T
First, the flow rate of PH ₃ is set to Vp1 while maintaining the temperature from the time when the temperature reaches 1 to the end of the vapor phase growth, and the TMI
When the time t3 has elapsed after the start of the supply of
And

(Sample 4) P as a temperature pattern (B)
The H ₃ supply pattern was set to (b). That is, while keeping the flow rate of PH ₃ at Vp2 all the time, the temperature of the substrate was kept at that temperature all the way from when the substrate temperature reached T1 until the vapor phase growth was completed. This processing condition is the same as the conventional growth condition for growing the InP buffer layer on the InP substrate by the low pressure MOCVD method.

(Discussion) The concentration of n-type carriers existing between the growth film and the substrate was measured for the above four samples, and as shown in Table 1, in Sample 1, 2.0 × 10 5 was obtained.
¹⁴ cm ⁻³ , 3.0 × 10 ¹⁵ cm ⁻³ for sample 2, 6.0 × 10 ¹⁵ cm ⁻³ for sample 3, 5.0 × 10 ¹⁶ cm ⁻³ for sample 4, , 3 clearly reduced the n-type carriers at the interface as compared with Sample 4.

Therefore, the inventor of the present invention conducted the above-mentioned experiment on the low pressure MOCVD method performed by the inventor and the atmospheric pressure MOCVD.
The method was compared and examined with the technique described in Japanese Patent Laid-Open No. 64-57711. Then, from the examination results, suitable heat treatment conditions for performing the low pressure MOCVD method were derived. The details of the examination are described below.

First, the heat treatment conditions of the technique disclosed in Japanese Patent Laid-Open No. 64-57711 are as follows. Processing temperature: 640 ° C. PH ₃ flow rate: 80 cc per minute Total flow rate of PH ₃ and H ₂ : 12 liters per minute Flow rate: 1 m / sec Pressure: 1 atm (ie 76 Torr) The flow rate of PH ₃ is 20% hydrogen base Since it is described that 400 cc of PH ₃ was flowed per minute, it was calculated by the following equation (1). 20% PH ₃ x 400 [cc / min] = 80 [cc / min] ... (1)

The inventor of the present invention estimates that the flow velocity is 1 m / s in error and 1 m / min in accuracy. The reason is that the cross-sectional area Scm ² and radius rcm of the reactor were calculated by the following equations (2) and (3) based on the above conditions, and the radius of the reactor was 1.5 cm, which was too small. Is. Therefore, the flow velocity is 1m / min.
When the cross-sectional area Scm ² and radius rcm of the reactor are calculated by the following equations (4) and (5), the radius of the reactor is 11.3 cm, which is an appropriate size, and the flow rate is 1 m / min. Is supposed to be reasonable. Therefore, in the following description, the flow velocity will be 1 m / min for the technique described in Japanese Patent Laid-Open No. 64-57711. S [cm ² ] = 12 [l / min] × (273 + 640) [K] / 273 [K] ÷ 1 [m / sec] = 6.7 [cm ² ] ... (2) r [cm] = √ (6.7 [cm ² ] ÷ π) = 1.5 [cm] ... (3) S [cm ² ] = 12 [l / min] × (273 + 640) [K] / 273 [K ] ÷ 1 [m / min] = 401 [cm ² ] ··· (4) r [cm] = √ (401 [cm ² ] ÷ π) = 11.3 [cm] ··· (5)

On the other hand, the heat treatment conditions of the experiment conducted by the present inventor were as follows. Processing temperature: 660 ° C. (samples 3, 4), 680 ° C. (samples 1, 2) PH ₃ flow rate: 400 cc / min (samples 2, 4), 80 / min
0 cc (Samples 1 and 3) Total flow rate of PH ₃ and H ₂ : 15 liters per minute Flow rate: 10 m per minute Pressure: 30 Torr Cross sectional area of reactor S: 1256 cm ² Radius r of reactor: 20 cm The flow rate of PH ₃ is: Since PH ₃ with 50% hydrogen base was flowed at 800 cc or 1600 cc per minute, it was calculated by the following equations (6) and (7), respectively. 50% PH ₃ x 800 [cc / min] = 400 [cc / min] ... (6) 50% PH ₃ x 1600 [cc / min] = 800 [cc / min] ... (7)

As can be seen from the above processing conditions, the reactor used by the present inventor has an area about three times larger than that of the reactor disclosed in the above-mentioned Japanese Patent Laid-Open No. 64-57711, and therefore, in the experiment by the present inventor. The flow rate of PH ₃ is JP-A-6
4-57711 PH ₃ flow rate is three times 240 per minute
It is considered to be equivalent in cc. However, comparing the case where the processing temperature is the same as the growth temperature of the normal InP buffer layer, 400 cc / min (240 cc of 1.67) of Sample 4 is compared.
2 times), there was no reduction effect of the n-type carrier, and the reduction effect was obtained at 800 cc / min of sample 3 (3.3 times 240 cc). From this, it was speculated that the low pressure MOCVD method was insufficient with the amount of PH ₃ that was considered to be effective in the atmospheric pressure MOCVD method.

Next, comparing the partial pressure of PH ₃ ,
The partial pressure of PH _{3 in} JP-A-64-57711 is 6.7 × 10 ⁻³ atm according to the calculation of the following formula (8), but for sample 3, it is 2. 2 × 10 ^-3 atm,
For sample 4, 1.1 × 10 ^{−3 is} calculated from the following equation (10).
It was atm. That is, it seems that if the partial pressure of PH ₃ is high, the effect of reducing n-type carriers can be obtained, but in another experiment conducted by the present inventor, the flow rate of PH ₃ was 400 cc / min, and the total pressure was 76 Torr. The partial pressure of PH ₃ is (1
From the calculation of the equation (1), the desired effect could not be obtained even at 2.7 × 10 ⁻³ atm. From this, it was found that the magnitude of the partial pressure of PH ₃ was not a direct factor for the effect of reducing n-type carriers. 80 [cc / min] ÷ 12 [l / min] × 1 [atm] = 6.7 × 10 ⁻³ [atm] ... (8) 800 [cc / min] ÷ 15 [l / min] × 30/760 [atm] = 2.2 × 10 ⁻³ [atm] (9) 400 [cc / min] ÷ 15 [l / min] × 30/760 [atm] = 1.1 × 10 ^-3 [atm] ... (10) 400 [cc / min] ÷ 15 [l / min] x 76/760 [atm] = 2.7 x ^10-3 [atm] ... (11)

From the results of the examination so far, it was found that the PH ₃ flow rate required per unit cross-sectional area of the reactor is different between the heat treatment under the normal pressure and the heat treatment under the reduced pressure. Therefore, when the PH ₃ flow rate per unit cross-sectional area of the reactor was determined for Samples 3 and 4, it was 0.64 cc / min / cm ² for Sample 3, and for Sample 4 the following ( From the calculation of formula 13), 0.32 cc / min / cm
^{Was 2} . Therefore, the critical value of the flow rate of PH ₃ per unit cross-sectional area for obtaining the desired effect by heat treatment under reduced pressure is 0.32 cc / min / cm ² and 0.64 cc / min / cm ²
It will be somewhere in between. The inventors further conducted an experiment to find the critical value, and found that the critical value was 0.50 cc / min / cm ² . That is, when the heat treatment temperature is the same as the growth temperature of the normal InP buffer layer, if the PH ₃ flow rate per unit cross-sectional area of the reactor is 0.50 cc / min / cm ² or more, the n-type carriers are reduced. It turned out that the effect was obtained. 800 [cc / min] / 1256 [cm ² ] = 0.64 [cc / min / cm ² ] ... (12) 400 [cc / min] / 1256 [cm ² ] = 0.32 [cc / Min / cm ² ] ・ ・ ・ ・ (13)

Next, with respect to the samples 3 and 4, the Si concentration at the interface between the growth film and the substrate was examined.
There was no obvious difference at about 2 × 10 ¹⁷ cm ⁻³ . From this, it was found that the effect of reducing n-type carriers at the interface was not brought about by the removal of Si.
That is, in the heat treatment under reduced pressure, unlike the case under normal pressure, it is considered that n-type carriers were reduced by some action other than Si removal. Regarding the action, even if the flow rate of PH ₃ is the same as that of sample 4 as in sample 2, the effect of reducing n-type carriers was obtained by increasing the heat treatment temperature to 680 ° C. Since the required PH ₃ flow rate differs between the
It is speculated that the radical hydrogen generated when ₃ is decomposed has some action.

As for the heat treatment time, the desired effect was obtained even if the heat treatment time was 15 minutes as in Sample 3. In another experiment conducted by the present inventor, the effect of reducing the n-type carrier was about the same between the sample having the heat treatment time of 15 minutes and the sample having the heat treatment time of 30 minutes. Therefore, when the present inventor further conducted an experiment to find a heat treatment time at which the reduction effect shows a saturation tendency,
The desired effect was obtained even in about 10 minutes. Therefore, it was found that the heat treatment time of 10 minutes or more is suitable.

Regarding the heat treatment temperature, Sample 1,
The desired effect was obtained at 660 ° C. and 680 ° C. from 2 and 3, but the present inventor further conducted an experiment to find the critical value of the heat treatment temperature for obtaining the effect.
It was confirmed that the heat treatment at 30 ° C was also effective. However, the heat treatment at a temperature higher than 700 ° C. is not preferable because the dissociation of P atoms from the InP substrate is significant and the substrate surface is roughened. Therefore, a suitable range of the heat treatment temperature is 630 to 700 ° C. It should be noted that the higher the heat treatment temperature is, the more excellent the effect of reducing the n-type carriers can be obtained, and that even if the heat treatment is performed at a temperature lower than the growth temperature (660 ° C.) of the InP layer, the vapor phase growth can be started. Since it has to be raised to the growth temperature, it is preferably at least the growth temperature, more preferably at a temperature 10 ° C. higher than the growth temperature (670 ° C.) or higher.

The reason why the heat treatment temperature is more preferably 670 ° C. or higher is according to another experiment conducted by the present inventor.
This is because if the temperature is equal to or higher than that temperature, the effect of reducing n-type carriers can be obtained even if the PH ₃ flow rate required per unit cross-sectional area of the reactor is 0.30 cc / min / cm ² . Sample 2 corresponds to this. However, the desired effect was not obtained when the PH ₃ flow rate was 0.20 cc / min / cm ² or 0.25 cc / min / cm ² .

The heat treatment temperature and the growth temperature in the above embodiment are values obtained by measuring the temperature on the back side of the substrate with a thermocouple.

Summarizing the results of the above examinations, the preferable heat treatment conditions are that the flow rate of PH ₃ is 0.50 SCCM / cm ² or more and the temperature is 630 ° C. or more and 700 ° C. or less (Sample 3 corresponds),
Also, the flow rate of PH ₃ is set to 0.30 SCCM / cm ² or more 67
Temperatures above 0 ° C and below 700 ° C (Sample 2 applies), P
The temperature of 670 ° C. or more and 700 ° C. or less (Sample 1 applies) when the flow rate of H ₃ is 0.50 SCCM / cm ² or more. By heat-treating the InP substrate under such conditions and then vapor-depositing a compound semiconductor layer such as InP, AlInP, or GaInAs on the InP substrate, n-type carriers existing at the interface between the growth film and the substrate can be removed from the conventional one. It is also possible to reduce In so that the n-type carriers at the interface between the growth film and the substrate are reduced by the low pressure MOCVD method.
A compound semiconductor layer can be grown on the P substrate.

The present invention can be applied not only under the reduced pressure of 30 Torr but also under the reduced pressure of 10 to 150 Torr. Needless to say, the size of the reactor is not limited to the size given in the above embodiment. Further, in each of the experiments of the above-described examples, the InP layer was vapor-phase grown on the InP substrate. However, the same effect is obtained when the compound semiconductor layer such as AlInP or GaInAs is vapor-phase grown on the InP substrate. An effect of reducing n-type carriers at the interface between the substrate and the growth film can be obtained.

[0031]

Claim 1 PH ₃ flow rates 0.50SCCM / cm ² or more as 630 ° C. or higher 700 ° C. temperature below the invention according according to the present invention, also the flow rate of PH ₃ in the invention of claim 2, wherein 0.30SCCM / Cm ² or more and a temperature of 670 ° C. or more and 700 ° C. or less, and in the invention of claim ₃ , the flow rate of PH ₃ is 0.50 SCCM / cm ² or more and a temperature of 670 ° C. or more and 700 ° C. or less. Then, by vapor-depositing a compound semiconductor layer of InP, AlInP, GaInAs, or the like thereon, the n-type carriers existing at the interface between the growth film and the substrate can be reduced more than in the conventional case, and thus low pressure MOCVD is performed. Method so that the number of n-type carriers at the interface between the growth film and the substrate becomes smaller than before.
A compound semiconductor layer can be grown on the InP substrate.

[Brief description of drawings]

FIG. 1 is a time chart showing a processing temperature and a flow rate of PH ₃ of each sample in an experiment conducted by the present inventor.

[Explanation of symbols]

Growth temperature for growing T1 InP buffer layer (660 ° C.) T2 Temperature higher than T1 (680 ° C.) Vp1 Vp2 double amount Vp2 InP buffer layer PH ₃ flow rate during growth

Claims (3)

[Claims] 1. When a compound semiconductor layer is vapor-phase grown on an InP substrate in a growth chamber in a reduced pressure atmosphere of 10 to 150 Torr, a PH per unit cross-sectional area of the growth chamber is increased.
PH ₃ and H ₂ with a flow rate of ₃ of 0.50 SCCM / cm ² or more
In the above atmosphere, after subjecting the InP substrate to a heat treatment at a temperature of 630 ° C. or higher and 700 ° C. or lower for 10 minutes or longer, the growth of the compound semiconductor layer is started. 2. When a compound semiconductor layer is vapor-deposited on an InP substrate in a growth chamber in a reduced pressure atmosphere of 10 to 150 Torr, the pH per unit cross-sectional area of the growth chamber is PH.
PH ₃ and H ₂ with a flow rate of ₃ of 0.30 SCCM / cm ² or more
In the above atmosphere, the InP substrate is subjected to heat treatment at a temperature of 670 ° C. or higher and 700 ° C. or lower for 10 minutes or longer, and then the growth of the compound semiconductor layer is started. 3. When the compound semiconductor layer is vapor-phase grown on the InP substrate in the growth chamber in a reduced pressure atmosphere of 10 to 150 Torr, the pH per unit cross-sectional area of the growth chamber is PH.
PH ₃ and H ₂ with a flow rate of ₃ of 0.50 SCCM / cm ² or more
In the above atmosphere, the InP substrate is subjected to heat treatment at a temperature of 670 ° C. or higher and 700 ° C. or lower for 10 minutes or longer, and then the growth of the compound semiconductor layer is started.